JP3476523B2 - Method and apparatus for reading data - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of recording data on an optical disk, and more particularly, 1
It relates to a method of positioning a portion of a track identified by one address.

[0002]

Data is recorded on concentric or spiral tracks. A spiral track may be considered a circle for addressing purposes because the track pitch is much smaller than its radius. Generally, each track is itself divided into segments or sectors, which are in turn divided into frames. The frame is a basic unit for actual data retrieval. It is self-contained in nature, that is, generally from a control mark for defining track centerline, clock and field sync information or a "servo" field containing preformatted pit and frame address information. By starting.

Since the number of frames recorded on a disc is large, addresses occupy a considerable part of the total space. As more and more frames are pushed into the disc, these addresses get longer, making it increasingly difficult to locate special parts of the optical head that move across the disc.

US Pat. No. 5,126,991 discloses a technique for speeding location identification by using a "creeping" code in the address. According to this technique, successive addresses are represented by codewords that differ only in one bit position. This improves the reliability of address identification when the scanning beam is not fixed at the center of a particular track.

According to the aforementioned patent, the address of the track is repeated at different positions along the track in order to speed up the identification and the correction of errors. Address multiplexing,
That is, the address is divided into a plurality of parts, and the so-called servo area of each frame includes only one of those parts, whereby the accuracy is remarkably improved.

One particularly improved method for identifying locations on a disc is the ANSI d document.
ocument X3B11 / 91 / 300-043, April 29, 1991). The mass formats described here (MA
SS FORMAT) uses pre-formatted address nibbles in servo areas of consecutive frames. When using the creeping code, the increasing address part can be used as a segment address. To do so, it is necessary to read out enough address nibbles to know the position of each frame in the segment and decode it to establish segment synchronization. That is, the position of the start point of the segment can be obtained from this information. Following this synchronization, the microprocessor can determine the location of other address bytes that follow.

[0007]

SUMMARY OF THE INVENTION The present invention aims to improve the speed of a segment by performing synchronization of the segments in the electronics of the drive before decoding.

[0008]

According to the invention, segment synchronization is obtained by a slight modification of the first control mark or pit located in the first frame of each segment. Instead of starting each frame from a "cosine" pit that is fixed at the fourth position or switches between the third and fourth positions, the cosine pit is the frame 0 of each segment (the first frame ) At position 3 of the BOS (starting point of the segment) pit and at position 4 of the next frame of the segment.

When reading a data disc according to the invention, if clock and frame synchronization has already been achieved, segment synchronization is achieved at the moment when the fourth bit of frame 0 is read.

In the preferred embodiment, the evaluation circuits are 3 and 4.
Check the signal amplitude at both positions. If the difference between the two is within a certain range, the reading is presumed to be valid.

In another embodiment, the BOS logic circuit is a BO
By counting the number of frame or channel bits between S pulses, it is checked whether BOS pulses are being generated at the correct intervals. If no BOS pulse is received due to an error or omission, the BOS logic inserts the pulse at the correct moment.

In yet another embodiment of the present invention, B is received when the command "perform a search for synchronization" is received.
The OS logic first looks for a valid BOS pulse (position 3). When the BOS pulse is detected, the frame counter is reset. For a 12-frame segment, after 12 frames, the frame counter sends a BOS interrupt to the microprocessor at the beginning of each frame 0. The microprocessor thereby checks the address bytes it receives from the address decoder. If the segment address byte is incremented, sync is valid and the frame counter continues cycling through 0-11. If the microprocessor does not understand the meaning of the address byte it is receiving, it issues another "Perform a search for synchronization" command.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a detected read scanning signal is supplied to a comparator 12, a memory 14 and an evaluation circuit 16. The memory 14 is, for example, a sample-and-hold circuit or a simple 1-bit clock period delay circuit. The output of the comparator 12 is supplied to the register 18. When the signal at position 4 is received at the input of the comparator, register 18 is clocked in no time.

BOS logic 22 receives the output of register 18 and checks whether the BOS pulses are occurring at the correct intervals by counting the number of frames or bits between BOS pulses. According to one aspect of the invention, after segment synchronization is achieved, if no BOS pulses are received from the bitstream from the detector, eg due to defects in the medium,
The BOS logic inserts a BOS pulse at the correct moment.

The evaluation circuit 16 measures the actual signal amplitude at both 3 and 4 positions. If the values are not above and below the predetermined threshold, respectively, the output of the comparator is ignored.

FIG. 2 shows the relative timing of the servo fields according to the present invention. The portion of frame 0 of one segment of track 30 is shown above the corresponding bit position of the frame after that segment and its adjacent tracks 31-34.

The servo field 100 of frame 0 has a BOS pit 102 at clock position 3 and a clock pit 104 at position 18. The wobble tracking pits 106 are alternately placed on both sides of the center line of the track 30, and the address nibble pits 110 and 112 are preformatted at the last 8-bit position of the servo field. These address nibbles are preferably arranged in a creeping code, so that only one or two bit transitions occur between one track and each adjacent track. This arrangement speeds up track identification during a search for a given track, as is well known.

The reference field 120 contains two recorded reference marks 122 and 124, which provide a reference for setting the detection threshold. The data field 130 preferably contains data recorded by a 1,7 RLL (run-length-limited) code.

Frame 2 of tracks 30-34 includes pits and marks at corresponding positions except for the first pit 202. A pit 202 is formed at bit position 4 to distinguish this pit, which functions as a cosine pit, from the BOS pit 102. A clock pit 204 is formed at the same bit position 18 as the other frames of each segment except the first frame.

Those skilled in the art will readily recognize that the present invention is applicable to many other code and format arrangements. For example, the code, bit position, and number of pits or blanks in a series are relatively arbitrary. The present invention is
It is not limited to using the wobble tracking servo pits, nor is it limited to the address given to the nibble. However, the present invention has the greatest utility in constructing an address code in which the frame number is not completely defined by the address. Such a configuration reduces the length of the servo field. However, this requires new segment synchronization for fast lock-on when searching for a given segment. Accordingly, the present invention has the scope as set forth in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram of a BOS logic circuit of the present invention.

FIG. 2 is a bit timing diagram in the record carrier of the present invention.

[Explanation of symbols]

12 comparator 14 memory 16 Evaluation circuit 18 registers 22 BOS logic circuit 30-34 truck 100 servo fields 102 BOS pit 104 clock pit 106 Wobble Tracking Pit 110 and 112 address nibble pits 120 reference fields 122,124 Reference mark 130 data fields 202 First Pit 204 clock pit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Johannes J. Ferboom 80908 Black Forest Juniper Drive, Colorado, United States 7555 (72) Inventor Fred N Wumble 80904 Colorado Springs W. Bijou 1518 (56) References 2-193359 (JP, A) JP-A-3-162720 (JP, A) JP-A-4-195775 (JP, A) JP-A-4-351761 (JP, A) Actual Kaihei 1-442446 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 20/10 G11B 20/12 G11B 20/14 G11B 7/00

Claims (14)

(57) [Claims] 1. Each track is divided into a plurality of segments, and each segment is divided into a plurality of frames,
A recording medium in which data is recorded as a pattern of marks arranged in parallel tracks, the data is recorded in at least some of the frames as a pattern of marks formed in bit positions, and each frame includes at least a first frame. Near the bit position, there is a control field containing control marks that define the position of the track and identify the frame, the two control marks in each control field having no other marks between them. A recording medium separated by a distance greater than a distance between adjacent other marks in the control field or in any of the patterns, scanning at least one mark in the control field;
And in a method of reading recorded data from a recording medium, the scanning determining a position of a first frame of a segment including the at least one control field, the first frame of each segment being defined. A control mark at a position and all other frames of the segment do not have a control mark at the defined position, and the position determining procedure detects that the control mark at the defined position is detected. A method of reading data, comprising: 2. A second of the two control marks is utilized for bit position clock synchronization, the control mark at the defined position being the first of the two control marks. The method for reading data according to claim 1, characterized in that. 3. In addition to the above, a BOS (beginning of) is further provided in response to detection of the control mark at the defined position.
segment: segment start point) pulse is generated, scanning is continued along the track including the segment including the at least one control field, the bit position that is the next fixed position is determined, and the next fixed position is determined. It is characterized by detecting whether or not there is a control mark at the determined position, and if the control mark is not present, the next BOS pulse synchronized with the next determined position is generated. Claim 2
The method of reading the data described in. 4. The data reading of claim 3, wherein the step of determining the position comprises counting bit positions from the defined position in synchronization with scanning along the track. Method. 5. An apparatus for reading data recorded as a pattern of marks arranged in parallel tracks on a recording medium in which each track is divided into a plurality of segments and each segment is divided into a plurality of frames. Data is recorded in at least some of the frames as a pattern of marks formed in bit positions, each frame having a control mark defining a track and identifying the frame, at least near the first bit position. Between two adjacent control marks in the control field or in any one of the control fields having two control marks in each control field with no other intervening marks between them. A means for scanning at least one mark of the control field at a distance greater than a distance of And means for determining the position of the first frame of the segment containing the at least one control field, the apparatus for reading the recorded data from the recording medium, the first of each segment in the recording medium. The frame has a control mark at a defined position, all other frames of the segment do not have a control mark at the defined position, and the means for determining the position is the control of the defined position. An apparatus for reading data, comprising a means for detecting a mark. 6. A device for reading data from the recording medium, wherein a second mark of the two control marks is at a clock bit position, the control mark being at a bit position directly adjacent to the defined position. Means for detecting the absence of the control mark at the defined position and the detection of the absence of the control mark at the bit position directly adjacent to the control mark, Means for generating a BOS pulse in response to the detection of the control mark.
A device for reading the data described in. 7. Means for determining a bit position that is the next defined position in response to a scan that is continued along a track that includes the segment that includes the at least one control field; Means for detecting the presence or absence of a control mark at a defined position and, in response to the absence of the control mark, generating the next synchronized BOS pulse corresponding to the next defined position. 7. The device for reading data according to claim 6, further comprising: 8. The method of claim 7, wherein the means for determining the position comprises a counter for counting the bit positions from the defined position in synchronization with the scanning performed along the track. A device for reading the described data. 9. A means for evaluating each signal detected at one of said defined positions and a position next to each of said defined positions, and said respective signal being in a predetermined range. 9. The apparatus for reading data according to claim 8, further comprising means for prohibiting the generation of a BOS pulse when there is no mutual relationship. 10. A means for evaluating each signal detected at one of said defined positions and a position next to each of said defined positions, and said respective signal having a predetermined range. BOS when there is no mutual relationship
The device for reading data according to claim 7, further comprising means for inhibiting generation of a pulse. 11. A means for evaluating each signal detected at one of said defined positions and a position next to each of said defined positions, and said respective signal having a predetermined range. BOS when there is no mutual relationship
7. The apparatus for reading data according to claim 6, further comprising means for inhibiting generation of a pulse. 12. A means for evaluating each signal detected at one of said defined positions and a position next to each of said defined positions, and said respective signal being in a predetermined range. BOS when there is no mutual relationship
The device for reading data according to claim 5, further comprising means for inhibiting generation of a pulse. 13. A recording medium in which each track is divided into a plurality of segments, each segment is divided into a plurality of frames, and data is recorded as a pattern of marks arranged in parallel tracks. Are recorded in at least some of the frames as a pattern of marks formed at the bit positions, each frame having a control field near the first bit position that includes a control mark that positions the track and identifies the frame. The two control marks in each control field have no other mark between them and the distance between adjacent control marks in the control field or in any of the patterns is greater than On recording media that are separated by a large fixed distance, the first frame of each segment has a control mark at a defined position. , All other frames of the segment recording medium characterized to have no control mark in a defined position said. 14. The second mark of the two control marks is a clock bit position, and the control mark at the defined position is the first mark of the two control marks. The recording medium according to claim 13.